In the fabrication of thin films such as metal films, magnetic films, coating films, vapor deposition films, and so on, the presence of holes (through holes) has a large impact on quality, and thus it is important to inspect for the presence of holes in the thin film being inspected. In conventional optical inspection devices that detect the presence of holes in the object being inspected, a light source and a photodetector are disposed on either side of the object being inspected and an optical detector detects the light beam that passes through the holes (through holes) in the object being inspected of the light beams emitted from the light source, thereby determining, based on the output of the detector, whether or not there are holes in the item being inspected. In addition, Japanese Patent Application Laid-open No. H 5-281156 discloses an optical inspection device that illuminates the object to be inspected while scanning the light, and uses a light-focusing optical system to focus the light that passes through the object to be inspected in order to detect, using a photodetector, the light thus focused.